Generally, through-silicon vias (TSVs) are formed in a semiconductor wafer by initially forming an opening at least partially through a substrate. A barrier layer is formed to line the opening in order to prevent a later-formed conductive material (e.g., copper) from diffusing into the substrate, where it might deteriorate the overall performance of other devices formed on the semiconductor wafer. As such, this barrier layer prevents damage caused by the conductive material.
TSV technology is important in creating 3D packages and 3D integrated circuits (IC). It provides interconnection of vertically aligned electronic devices through internal wiring that significantly reduces complexity and overall dimensions of a multi-chip electronic circuit.
A typical TSV process includes formation of TSV holes and deposition of a diffusion barrier layer and a conductive seed layer. A conductive material is then electroplated (deposited) into TSV holes. Copper is typically used as the conductive material as it supports high current densities experienced at complex integration, such as 3D packages and 3D integrated circuits, and increased device speed. Furthermore, copper has good thermal conductivity and is available in a highly pure state. As the trend towards more complexity and higher performance of electronics continues, it is therefore desirable to have improvements in the fabrication of TSVs.
A first aspect of the present invention includes method of forming a semiconductor structure, comprising: depositing a dielectric layer on a bulk silicon substrate; forming an opening in the dielectric layer; depositing a silicon nitride layer on the dielectric layer; forming a through-silicon via cavity; applying a sacrificial layer to sidewalls of the through-silicon via cavity; depositing a conductor in the through-silicon via cavity to form a through-silicon via; performing a backside thinning process to expose the sacrificial layer; removing the sacrificial layer; and applying a sealant dielectric layer.
A second aspect of the present invention includes a method of forming a semiconductor structure, comprising: depositing a silicon oxide layer on a bulk silicon substrate; forming an opening in the silicon oxide layer; depositing a silicon nitride layer on the silicon oxide layer; forming a through-silicon via cavity; applying a sacrificial layer to sidewalls of the through-silicon via cavity; applying a barrier layer on the sacrificial layer; depositing copper in the through-silicon via cavity to form a through-silicon via; performing a backside thinning process to expose the sacrificial layer; removing the sacrificial layer with a hydrofluoric acid etchant; applying a sealant dielectric layer; and terminating the through-silicon via.
A third aspect of the present invention includes A semiconductor structure comprising: a bulk silicon substrate; a through-silicon via formed in the bulk silicon substrate; a barrier layer disposed adjacent to the through-silicon via; and an air gap disposed adjacent to the barrier layer.